Flow adjusting valve and die casting machine incorporating the same

Abstract

A flow adjusting valve of the spool type having a flow inlet and a flow outlet incorporated in a die casting machine comprising an injection cylinder for activating a plunger by a pressurized oil, a pressurized oil source, a single hydraulic passage through which the oil is supplied from the oil source to the cylinder, so that the single passage includes the valve therein in such arrangement that upstream and downstream portions of the single passage communicate with the flow inlet and the flow outlet, respectively, whereby the injection operation is switched from low speed injection to high speed injection. The valve comprises a valve body having the above flow inlet and outlet and a valve bore being formed with or without a cylindrical sleeve having at least a radial hole, so that the valve bore communicates with the flow inlet and the flow outlet; a valve spool comprised of a cylindrical rod axially slidably mounted in a tight manner in the valve bore for closing and opening the flow outlet by axial forward and rearward movement thereof relative to the valve body; a screw mechanism, preferably a ball screw mechanism, provided at the rear end of the valve body for transforming rotational movement into axial movement; and a motor capable of controlling the amount of rotation, preferably a pulse motor, provided for driving the valve spool via the screw mechanism, so that the valve spool is forced to move in the axial direction relative to the valve body.

I claim: 
     
       1. A spool-type flow adjusting valve comprising: a valve body having a flow inlet and a flow outlet for transferring a pressurized fluid within said valve;   A valve bore formed within said valve body to communicate with said flow inlet and said flow outlet and having a first and a second chamber at opposite ends of said valve bore, said flow inlet being connected to said first chamber;   a valve spool slidably positioned within said valve bore and maintaining frictional engagement therewith, said valve spool having a cylindrical rod for slidably positioning said valve spool along the axis of said rod between said first and said second chambers, the surface area of said valve spool facing said first chamber being greater than the surface area of said valve spool facing said second chamber, the opening and closing of said flow outlet being dependent upon the reciprocating movement of said valve spool within said valve bore;   means for slidably positioning said cylindrical rod; and   at least one flow passage formed within said valve spool for interconnecting said first and second chambers, said flow passage being defined by a through-hole formed along the length of said valve spool, wherein the flow of the fluid passing between said flow inlet and said flow outlet increases as said valve spool moves in the direction of said second chamber and opens said flow outlet; and   a groove between the outer surface of said valve spool adjacent said valve bore and said flow passage for allowing the fluid to flow from said flow passage and into said flow outlet when said groove is aligned with said flow outlet, and wherein said flow outlet includes first and second channels extending substantially perpendicular to the axis of said valve spool, said first channel being in fluid communication with said first chamber and said second channel for fluid communication with said flow outlet when said groove is aligned with said second channel, each of said first and second channels having a circumferential cut-out section along said valve bore for communicating said fluid from said first chamber to said first and second channels when said cut-out sections are uncovered by movement of said valve spool, and wherein the difference between the surface area of said valve spool facing said first chamber and the surface area of said valve spool facing said second chamber produces a pressure differential at the opposing surfaces of said valve spool for generating thrust forces for positioning said valve spool within said valve bore.   
     
     
       2. The spool-type flow adjusting valve as defined in claim 1, wherein said means for slidably positioning said cylindrical rod includes: a housing mounted adjacent said second chamber of said valve bore, the adjacent surfaces of second chamber and said housing having shaft receiving means coaxially aligned with said cylindrical rod;   a connecting shaft slidably supported within said shaft receiving means and having a rod portion and a cylindrical portion, said rod portion being connected to said valve spool;   motor means having a driving member and a driven member mounted within said housing for imparting rotational movement within said housing; and   conversion means connecting said cylindrical portion of the connecting shaft to said driven member for transforming rotational movement into reciprocating movement, said conversion means including a nut attached to said cylindrical portion, a drive shaft connected to said driven member for rotation within said nut, and means for preventing said nut from rotating relative to said housing.   
     
     
       3. The spool-type flow adjusting valve as defined in claim 2, wherein balls are rotatably positioned between said nut and said screw drive shaft, and wherein said motor means includes a pulse motor. 
     
     
       4. The spool-type flow adjusting valve as defined in claim 3, wherein said rotation prevention means includes a means projecting from said nut and a slot formed by said housing and extending a predetermined distance substantially parallel to the axis of said drive shaft, said projection being slidable within said slot. 
     
     
       5. The spool-type flow adjusting valve as defined in claim 4, wherein said cylinder portion includes a plurality of perforations disposed in spaced and angled intervals about the circumference of said cylinder portion. 
     
     
       6. The spool-type flow adjusting valve as defined in claim 4, wherein said conversion means includes a sensor having a magnetic element affixed to said nut, and switch means attached to said housing for detecting the position of said magnetic element, said switch means providing feedback to said motor for controlling the axially sliding movement of said valve spool. 
     
     
       7. The spool-type flow adjusting valve as defined in claim 4, wherein said flow passage is proximate the periphery of said valve spool.